Novel preparation of bromonitro alcohols

ABSTRACT

A novel process for preparing bromonitro alcohols of the formula WHEREIN R1 is selected from the group consisting hydrogen, methyl and halogenated methyl and R2 is selected from the group consisting of hydrogen and methyl and ethyl which may be substituted with at least one hydroxy group comprising reacting an aldehyde with a nitroalkane in the presence of an aqueous alkali metal hydroxide and reacting the reaction product with bromine at temperatures below 25* C.

[22] Filed:

United States Patent 1 Wessendorf NOVEL PREPARATION OF BROMONITRO'ALCOHOLS [30] Foreign Application Priority Data Oct. 28, 1969 Germany ..P 19 54 W32 [52] US. Cl ..260/633 [5 l] ..C07c 31/34 [58] Field of Search ..260/633 [56] References Cited UNITED STATES PATENTS 2,l23,556 7/l938 Nicodemus ..260/633 3,534,112 l0/l970 Tindall ..260/638 N FOREIGN PATENTS OR APPLICATIONS 1261 ,278 2/1968 Germany ..260/633 Jan.16,1973

OTHER PUBLlCATlONS Eckstein et al., J. Chem. Soc. (1961) p. 1375 Primary Examiner-Howard -T. Mars Attorney-Hammond & Littell ABSTRACT I v A novel process for preparing bromonitro alcohols of the formula Ilia R|CHCN0z H Br' I wherein R is selected from -the groupconsisting" hydrogen, methyl and halogenated methyl and R is selected from the group consisting of hydrogen and methyl and ethyl which may be substituted with at least one hydroxy group comprising reacting an aldehyde with a nitroalkane in the presence of an aqueous alkali metal hydroxide and reacting the reaction product with bromine at temperatures below 25C.

9 Claims, No Drawings NOVEL PREPARATION OF BROMONITRO ALCOHOLS STATE OF THE ART The prior preparation of bromonitro alcohols of formula l was previously effected by reacting a nitromethane with an aldehyde and reacting the reaction product with the sodium salt of a nitroalcohol in an alcoholic solution to obtain a nitroalcohol which was then reacted with bromine in an organic solvent such as ether, chloroform or carbon tetrachloride to form the bromonitro alcohol. The reaction scheme is illustrated as follows:

-tained with short chain nitroalkanes, particularly with Attempts to scale up the said process from the laboratory stage to plant scale have met with considerable difficulties. The use of readily combustible solvents such as ethanol or ether is only possible if special precautions are taken to prevent explosions or inhalation of the solvents. The preparation of sodium alcoholate solutions from metallic sodium and alcohol which must be freshly prepared for optimum yields also requires special precautions to avoid dangers. The use of commercially available sodium ethylate or sodium methylate or sodium methylate solutions lead to considerable losses in the process yields.

The isolation of the sodium salts of the nitroalcohols in step B of the above reactions also causes great difficulties. Both the filtration and purification of the said salts are very time consuming even in small batches. Moreover, the said sodium salts are not very stable and when held in the air, decomposition begins after a short time with formation of a yellow color. Heating or a slight blow to the said salts can lead to a spontaneous decomposition of the salts.

To avoid these difficulties, attempts have been made to effect the bromination step before the added condensation by first brominating the nitroalkane to form the corresponding bromonitro alkane and reacting. the latter with the aldehyde to form the bromonitro alcohol. While this process is quite good in the case of long chain nitroalkanes, unsatisfactory results are obnitromethane. For example, bromination nitromethane in carbon disulfide resulted in a 40 percent yield of the bromonitro methane which could then be reacted with formaldehyde to form 2-bromo-2- nitro-propane-diol. This reaction does not eliminate the dangers involved in the use of highly combustible solvents.

Another process proposed for the production of bromonitro alcohols to avoid the isolation of inter mediates and the use of dangerous products comprises reacting a nitroalkane, an aldehyde and calcium hydroxide or calcium chloride and sodium hydroxide to form a solution or suspension of a calcium salt of the desired nitroalcohol to which bromine is added to effect the bromination. This process was based on the unexpected discovery that magnesium salts or alkaline earth metal salts, such as the calcium salt, of nitroalcohols can be prepared due to their slight solubility at a pH of about 7 directly without isolation of intermediate stages from the nitroalkane, aldehyde and suitable inorganic salt. Moreover, the aqueous suspension could be brominated without intermediate isolation to obtain the corresponding bromonitro alcohol.

An improvement of this process to avoid formation of undesired by-products was effected by effecting bromination by adding the solution or suspension of the calcium salts into the given amount of bromine rather than by adding bromine to the solution or suspension of the calcium salts as done previously. However, this process has been found to be commercially advantageous only when a solution of the calcium salt of the nitroal cohol is formed which can be introduced without difficulty into the bromine. 'However, if a sparingly soluble precipitate of the calcium salt is formed so that the salt must be added almost completely as a suspension to the bromine, the bromination stage has serious difficulties.

OBJECTS OF THE INVENTION It is an object of the invention to provide a novel process for the preparation of bromonitro alcohols without the use of highly combustible solvents.

It is a further object of the invention to provide a novel commercial process for the preparation of bromonitro alcohols without the problem of isolating unstable intermediate products.

These and other objects and advantages of the invention will become obvious from the following detailed description.

THE INVENTION The novel process of the invention for the preparation of bromonitro alcohols of the formula wherein R is selected from the group consisting of hydrogen, methyl and halogenated methyl and R is selected from the group consisting of hydrogen and methyl and ethyl which may be substituted with at least one hydroxy group such as the R,-CHOl-l-group comprises reacting an aldehyde of the formula wherein R, is selected from the group consisting of hydrogen, methyl and halogenated methyl with a nitroalkane of the formula R -CH NO wherein R is selected from the group consisting of hydrogen, methyl and ethyl and an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide in the presence of water to obtain an aqueous solution of the alkali metal salt of the nitroalcohol and reacting at a temperature less than 25 C. the said aqueous solution with the given amount of bromine. The aqueous solution may be added to the bromine, or simultaneously the said solution and the given amount of bromine can be added to an inert organic solvent.

Preferably, the process is effected by mixing all the aldehyde with a portion of the nitroalkane and a small amount of the alkali metal hydroxide in solution to start the reaction which is indicated by a sharp rise in the temperature and then the reaction is completed while cooling by adding the rest of the nitroalkane and the sodium hydroxide solution whereby an aqueous solution of the alkali metal salt of the nitroalcohol is formed which can be reacted with the bromine. While sodium is preferred, other alkali metals such as potassium hydroxide can be used.

Since sodium salts of nitro alcohols were known from the literature to be unstable, serious doubts existed concerning the possibility of using the said salts as intermediates for the preparation of bromonitro alcohols, especially in view of their sensitivity to heat. It was, therefore, surprising that in the reaction indicated above in aqueous solution the sodium salts of the nitroalcohols did not decompose and gave yields of bromonitro alcohols which in many cases exceeded the yields obtained by the calcium salt reaction. For example, l-bromo-l-nitro-propanol-2 can be prepared by the process of the invention in 82 percent yields as compared to the 73 percent yields of the calcium salt process.

Examples of suitable aldehydes for the process of the invention are formaldehyde, acetaldehyde, monochloro, dichloro, and trichloro-acetaldehyde. Suitable nitromethanes are nitro methane, nitro ethane and l-nitro propane. The amounts of nitroalkane and aldehyde used depend upon the desired nitroalcohol and are preferably in stoichiometric amounts for monohydroxy alcohols and for dihydroxy alcohols, twice the molar amount of aldehyde is used. The amount of sodium hydroxide solution used is the amount necessary to form the sodium salt of the nitro alcohols.

To effect the bromination, the aqueous solution of the sodium salt of nitro alcohol is added to the necessary amount of bromine which is preferably dissolved in a halogenated hydrocarbon such as ethylene chloride, methylene chloride or chloroform. The rate of addition depends upon the removal of the heat of reaction so that the temperature does not rise above 25C, preferably in the range of to 20C. The end of the bromination is easily recognized by the disappearance of the bromine color.

The process can also be carried out continuously. The bromination can also be effected by simultaneously adding the aqueous solution of the alkali metal salts and bromine with stirring to an inert organic solvent such as a halogenated hydrocarbon at temperatures not above 25C. The bromine should then be maintained in an excess as can be seen from the color of the solvent.

The bromonitro alcohol can be recovered in known ways by recrystallization or distillation. However, in many cases no purification of the products is required.

The said bromonitro alcohols have antimicrobic activity with a broad spectrum of activity, short kill times and low inhibiting concentrations.

In the following examples there are described several preferred embodiments to illustrate the invention. However, it is to be understood that the invention is not intended to be limited to the specific embodiments.

EXAMPLE 1 2-Bromo-Z-Nitro-Propane-Diol-l ,3

A mixture of 86 gm (1.05 moles) ofa 37 percent formaldehyde solution and 25 gm of nitro-ethane were stirred while dropping therein 10 cc of a sodium hydroxide solution prepared from 40 gm (1 mole) of sodium hydroxide and 200 cc of water during which time the temperature rose to 55C. After cooling the mixture to 40C, an additional 54 gm (total of 1.05 mole) of nitro-ethane were added dropwise while keeping the temperature at 40C. and then stirring was continued for 30 minutes at 40C. 150 cc of water were then added to the reaction mixture which was cooled to 20C. The remainder of the sodium hydroxide solution was then added with stirring while keeping the temperature at 20C and the mixture was stirred for another 30 minutes.

The resulting clear solution and 159.8gm (1 mole) of bromine were simultaneously added with stirring to 200 cc of carbon tetrachloride while keeping the temperature at 10C and always maintaining an excess of bromine as indicated by the color. At the end of the ad dition of the reactants, the reaction mixture was colorless. The lower phase was decanted and the solvent was distilled off to obtain 177.5 gm of 2-bromo-2-nitropropanol melting at 33.3 5C.

EXAMPLE ll 1-Bromo-1-Nitro-Propanol-2 A mixture of 48.5 gm (1.1 moles) of acetaldehyde and 20 gm of nitromethane were stirred in an apparatus equipped with a reflux condenser and then 3 cc of a sodium hydroxide solution prepared from 40 gm 1 mole) of sodium hydroxide and 200 cc of water were added dropwise to the stirred mixture during which the temperature rose to C. After cooling the mixture to 60C, another 41 gm (total of 1 mole) of nitromethane were added and the mixture was stirred for another 30 minutes at 60C. The mixture was then cooled to 20C and cc of water were added followed by dropwise addition of the rest of the sodium hydroxide solution while keeping the temperature at 20C.

The resulting solution was reacted with bromine as in Example 1 to obtain 181.3 gm (98.5 percent yield) of raw product which was then subjected to distillation to obtain 148.3 gm (82 percent yield) of l-bromo-l-nitropropanol-Z having a boiling point of 56C at 0.01 mm Hg and a refractive index n 1.4932.

EXAMPLE Ill 2-Bromo-2-Nitro-Propane-Diol-l ,3

40 gm (1 mole) of sodium hydroxide were dissolved in 800 cc of water and 150 cc of the resulting solution were added with stirring to 163 gm (2 moles) of a 37 percent formaldehyde solution.- Then, 61 gm (1 mole) of nitromethane were added with stirring while keeping the temperature not above 30C and after cooling to 20C, the balance of the sodium hydroxide solution was added while keeping the temperature at 20C.

The bromination was effected as in Example 1 except that the carbon tetrachloride was replaced by ethylene chloride to obtain 168 gm (84% yield) of 2-bromo-2- nitro-propanediol-l ,3 melting at 1 18C.

EXAMPLE 1V l-Bromo-l-Nitro-3,3,3-Trichloropropanol2 165.5 gm (1 mole) of chloral hydrate were admixed with stirring with 18 gm (1 mole) of water and the mixture was heated to 55C. 15 gm of nitromethane were added with stirring to the mixture during which the temperature rose to 75C. 20 cc of a sodium hydroxide solution prepared from 40 gm (1 mole) of sodium hydroxide and 200 cc of water were added to the reaction mixture and then another 44 gm (total of 1 mole) of nitromethane were added dropwise with stirring and slight cooling. The mixture was stirred for 30 minutes at 60C and after cooling to 20C, 400 cc of water and then the balance of the sodium hydroxide solution was added with cooling.

The resulting solution was then brominated as in Example l to obtain 281 gm (98 percent yield) of crude product which upon distillation yielded 247 gm (86 percent yield) of 1-bromo-l-nitro-3 ,3 ,3- trichloropropanol-2 having a boiling point of 7678C at 10 mm Hg. and a refractive index n 1.5376.

Various modifications of the process of the invention may be made without departing from the spirit or scope thereof and it should be understood that the invention is intended to be limited only as defined in the appended claims.

I claim:

1. A process for the preparation of bromo-nitro al-' cohols of the formula v wherein R is selected from the group consisting of hydrogen, methyl and chlorinated methyl and R is selected from the group consisting of hydrogen and methyl and ethyl which may be substituted with a hydroxy group comprising reacting an aldehyde of the formula wherein R is selected from the group consisting of hydrogen, methyl and chlorinated methyl with av bromine is effected between 0 and 20C.

4. The process of claim 1 wherein the aldehyde [8 formaldehyde.

5. The process of claim 1 wherein the nitroalkane is nitromethane.

6. The process of claim 1 wherein the aqueous solution and bromine are added simultaneously to an inert organic solvent while maintaining an excess of bromine in the solvent.

7. The process of claim 1 wherein theaqueous solution is added to bromine in an inert organic solvent.

8. The process of claim 1 wherein the aldehyde,

nitroalkane and alkali metal hydroxide are present in stoichiometric amounts.

9. The process of claim 1 wherein there are two moles of aldehyde per mole of nitroalkane. 

2. The process of claim 1 wherein the alkali metal hydroxide is sodium hydroxide.
 3. The process of claim 1 wherein the reaction with bromine is effected between 0* and 20*C.
 4. The process of claim 1 wherein the aldehyde is formaldehyde.
 5. The process of claim 1 wherein the nitroalkane is nitromethane.
 6. The process of claim 1 wherein the aqueous solution and bromine are added simultaneously to an inert organic solvent while maintaining an excess of bromine in the solvent.
 7. The process of claim 1 wherein theaqueous solution is added to bromine in an inert organic solvent.
 8. The process of claim 1 wherein the aldehyde, nitroalkane and alkali metal hydroxide are present in stoichiometric amounts.
 9. The process of claim 1 wherein there are two moles of aldehyde per mole of nitroalkane. 